Halation-prevention filter, image analysis device equipped with said halation-prevention filter, and diffraction pattern intensity analysis method and diffraction pattern intensity correction program that use said halation-prevention filter

ABSTRACT

An image analysis device  1  is equipped with the photoreceptive means  11  that optically acquires diffraction pattern A that appears on the fluorescent screen  24  in order to obtain the diffraction pattern resulting from reflection high-energy electron diffraction, and the halation-prevention filter  12  provided so as to transmit the visible light emitted from the diffraction pattern A of the fluorescent screen  24 , along the light path connecting the photoreceptive means  11  and the fluorescent screen  24 . Also, the filter  12  is varied so that the transmittance of the visible light transmitted through the filter  12  is minimum at the filter center and increases with the distance from the center.

REFERENCE TO RELATED APPLICATIONS

This is a divisional patent application of application Ser. No.10/136,542, filed May 1, 2002, now abandoned, entitled“HALATION-PREVENTION FILTER, IMAGE ANALYSIS DEVICE EQUIPPED WITH SAIDHALATION-PREVENTION FILTER, AND DIFFRACTION PATTERN INTENSITY ANALYSISMETHOD AND DIFFRACTION PATTERN INTENSITY CORRECTION PROGRAM THAT USESAID HALATION-PREVENTION FILTER”, which claimed an invention which wasdisclosed in Japanese application number 2001-325324, filed Oct. 12,2001. The benefit under 35 USC §119(a) of the Japanese application ishereby claimed, and the aforementioned applications are herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device that analyzes diffractionpatterns resulting from reflection high-energy electron diffraction andan intensity analysis method, and it particularly relates to ahalation-prevention filter that prevents diffraction pattern halation,an image analysis device equipped with the halation-prevention filter,and a diffraction pattern intensity analysis method and a diffractionpattern intensity correction program that use the halation-preventionfilter.

2. Description of Related Art

Reflection high-energy electron diffraction is an analytical techniquewidely used in the molecular beam epitaxy field, as a technique formonitoring in real time the growth state, when growing crystals (e.g.,metals, semiconductors) in vacuo.

In particular, ever since it was discovered that theatomic-layer-by-atomic-layer growth of crystals was observable bymeasuring the intensity of specular reflection point(s) in reflectionhigh-energy electron diffraction, reflection high-energy electrondiffraction has been recognized as a useful method for controllingcrystal growth at the atomic layer level, so it has been applied tovarious industries (e.g., semiconductor device fabrication).

However, in image analysis devices that use the diffraction patternsresulting from conventional reflection high-energy electron diffraction,when a diffraction pattern is photographed, the intensities of thespecular reflection point(s) are much greater than the intensities ofthe surrounding diffraction points and Kikuchi pattern, so the vicinityof the specular reflection point(s) produces halation. This becomesparticularly significant when the entire diffraction pattern isphotographed, and if the light exposure is decreased during photographyin order to avoid halation, the following drawback results: thesurrounding diffraction points and the Kikuchi pattern becomeunobservable because of the insufficient intensity (light intensity).

This problem frequently restricts, to the region between the specularreflection point(s) and the zero-order Laue zone, the conventional CCDcamera-based observation of the diffraction pattern resulting fromreflection high-energy electron diffraction, as the only way to avoidhalation without decreasing the light exposure. However, when such anobservation technique is used, the diffraction pattern information fromoutside the zero-order Laue zone is undetected, so a problem differentfrom the aforementioned drawback is confronted: it is impossible toaccurately analyze the sample state.

In a technique sometimes adopted in order to prevent the halation thatoccurs in a diffraction pattern when using a camera to photograph thediffraction pattern resulting from reflection high-energy electrondiffraction, masking is performed when printing the photographicprinting paper instead of in the photography state, thereby yielding adiffraction pattern with good contrast. This technique has a problem,however, in that linear intensity analysis is impossible because anirreversible correction is applied to the light intensity, which isessential for intensity analysis.

As another device configuration measure that prevents halation, there isa technique that uses sectors with a masking part and a transmissivepart, between the fluorescent screen and the measurement sample in thevacuum chamber. To be more specific, in a sector, the masking part isconfigured by using a blade or vane with a geometrically computed shape.Furthermore, by making the electron beam, which is diffracted in thevicinity of the surface of the measurement sample, pass through thesector in which this blade rotates, the sector functions to inhibithalation near the center by physically decreasing the amount of electronbeam passing through.

Actually, however, the mere adherence of minute dust particles on theblade markedly attenuates the intensity in the rotating partcorresponding to this dust's position. An a result, this intensityattenuation affects the electron beam that forms the diffractionpattern, so the diffraction pattern does not accurately reflect thestructure of the material. Consequently, not only must the blade bemanufactured precisely, but it must be clean. Actually, however, theincreased complexity of the adopted rotary mechanism also adds to thedifficulty of completely eliminating dust, etc. From the standpoint ofmeasurement precision, therefore, diffraction intensity analysis bymeans of such sectors set in vacuo is undesirable.

Furthermore, although Japanese Unexamined Patent Publication No. 7-6967discloses an observation device that uses reflection high-energyelectron diffraction, it merely suggests a configuration that uses afilter that selectively transmits only light of a specific wavelength.That is, it is based on the idea of handling as a bundle the lightincident on the filter, but there is no suggestion of the idea ofincrementally varying the light transmittance.

SUMMARY OF THE INVENTION

The present invention relates to a device that analyzes diffractionpatterns resulting from reflection high-energy electron diffraction andan intensity analysis method, and it particularly relates to ahalation-prevention filter that prevents diffraction pattern halation,an image analysis device equipped with the halation-prevention filter,and a diffraction pattern intensity analysis method and a diffractionpattern intensity correction program that use the halation-preventionfilter. The halation-prevention filter is configured such that atransmittance of the visible light transmitted through the filter islowest at a center of said filter and increases with a distance fromsaid center. The present invention implements image analysis thatenables the acquisition of diffraction patterns without halation andwith good contrast. It also aims at implementing image analysis thatenables the analysis of the intensity at all points in an obtaineddiffraction pattern.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an overall schematic diagram showing one example of theimage analysis device of the first embodiment of the present invention.

FIG. 2 shows a photograph showing one example of the halation-preventionfilter shown in FIG. 1.

FIG. 3 shows an overall schematic diagram showing one example of theimage analysis device of the second embodiment of the present invention.

FIG. 4 shows a schematic diagram showing one example of the imageanalysis device of the third embodiment of the present invention.

FIG. 5 shows a functional block diagram of the diffraction patternintensity correction means equipped with the image analysis device shownin FIG. 4.

FIG. 6 shows a data structure diagram for the measurement intensitystorage means equipped with the diffraction pattern intensity correctionmeans shown in FIG. 5.

FIG. 7 shows a functional block diagram showing an example of thedeformation of the diffraction pattern intensity correction means shownin FIG. 5.

FIGS. 8(a) through 8(c) show photographs showing an example of thediffraction pattern, which were photographed without using thehalation-prevention filter of the present invention.

FIG. 9 shows a photograph showing an example of the diffraction patternphotographed by using the halation-prevention filter of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

To achieve the purposes, the present invention adopts ahalation-prevention filter that is provided so as to transmit thevisible light emitted from the diffraction pattern of the fluorescentscreen, along the light path that connects the fluorescent screen onwhich the diffraction pattern appears as the result of reflectionhigh-energy electron diffraction and the photoreceptive means thatoptically acquires the diffraction pattern. Also, the transmittance ofthe visible light transmitted through the filter is varied so as to belowest at the center of the filter and to increase with the distancefrom the center.

According to the present invention, by varying the filter transmittanceso that it is lowest at the filter center and increases with thedistance from the center, it is possible to decrease the centralintensity, thereby minimizing the difference in intensity between thecenter and the peripheral areas, even for diffraction patterns with ahigh central intensity.

Also, in the present invention, the configuration is such that thetransmittance increases in proportion to r^(n), where r is the distancefrom the filter center.

According to the present invention, the transmittance increases inproportion to the n^(th) power of r, the distance from the filtercenter, so the present invention can eliminate the smoothing orflattening of transmittance near the center, in intermediate regions,and elsewhere.

The present invention also adopts an image analysis device equipped witha photoreceptive means that optically acquires the diffraction patternappearing on the fluorescent screen used to obtain the diffractionpattern resulting from reflection high-energy electron diffraction, andit adopts a halation-prevention filter that is provided so as totransmit the visible light emitted from the diffraction pattern of thefluorescent screen, along the light path connecting the photoreceptivemeans and the fluorescent screen.

The filter varies the transmittance of the visible light transmittedthrough the filter, so that it is lowest at the center of the filter andincreases with the distance from the center.

According to the present invention, by varying the filter transmittanceso that it is lowest at the filter center and increases with thedistance from the center, it is possible to decrease the centralintensity, thereby minimizing the difference in intensity between thecenter and the peripheral areas, even for diffraction patterns with highcentral intensity.

The invention is configured so that the transmittance increases inproportion to r^(n), where r is the distance from the filter center.

According to the present invention, the transmittance increases inproportion to the n^(th) power of r, the distance from the filtercenter, so the present invention can eliminate the smoothing oftransmittance near the center, in intermediate regions, and elsewhere.

The invention is also configured so that it has an in-plane or in-planarmovement means that moves the halation-prevention filter in the planeorthogonal to the light path.

The present invention has an in-plane or in-planar or in-planar movementmeans, so it is possible to move the center of the halation-preventionfilter.

The invention is also configured so that, in the image analysis devicedescribed, it is equipped with a photoemissive means that generates apoint light source; an emission control means that controls thegeneration of the point light source of the photoemissive means; anintensity measurement means that measures, via the photoreceptive means,the intensity of the visible light emitted from the diffraction patternof the fluorescent screen as well as the intensity of the visible lightemitted from the point light source, that passes through the filter; anintensity decrease rate computation means that computes the rate ofdecrease in the intensity of the visible light transmitted through thefilter, based on the intensity of the visible light emitted by the pointlight source, that was measured by the intensity measurement means; anda corrected-intensity computation means that computes the correctedintensity used to correct the intensity of the visible light emittedfrom the diffraction pattern of the fluorescent screen, that wasmeasured by the photoreceptive means.

According to the present invention, the rate of decrease in theintensity of the visible light transmitted through the filter iscomputed, and, based on the rate of decrease, the corrected intensityresulting from the correction of the intensity of the visible lightemitted from the diffraction pattern of the fluorescent screen iscomputed, so it is possible to obtain the intensity of the visible lightactually emitted from the diffraction pattern of the fluorescent screen.

The invention also adopts the diffraction pattern intensity analysismethod used to analyze the intensity of the visible light emitted fromthe diffraction pattern of the fluorescent screen as a result ofreflection high-energy electron diffraction; and the method has aprocess that utilizes the photoreceptive means to measure the intensityof the diffraction pattern that appears on the fluorescent screen, via ahalation-prevention filter such that the transmittance is minimum at thefilter center and the transmittance increases with the distance from thecenter; a process that utilizes the photoreceptive means to measure theintensity of the point light source, via the filter, and obtains therate of decrease in the intensity of the visible light transmittedthrough the filter, based on the measured results; and a process that,based on the rate of decrease, corrects the diffraction patternintensity that was measured by the photoreceptive means.

According to the present invention, it is equipped with a process thatmeasures the intensity of the diffraction pattern, via ahalation-prevention filter that is varied so that the transmittanceincreases with the distance from the center, a process that obtains therate of decrease in the intensity attributable to the filter, and aprocess that corrects the intensity of the diffraction pattern based onthe decrease rate, so it is possible to obtain the intensity of thevisible light actually emitted from the diffraction pattern.

The invention is configured so that the transmittance of the visiblelight transmitted through the filter increases in proportion to then^(th) power of r, where r is the distance from the filter center.

According to the present invention, the transmittance increases inproportion to the n^(th) power of r, the distance from the filtercenter, so it is possible to optimally control the contrast over theentire diffraction pattern.

The invention implements a measured intensity storage means that storesthe intensity of the visible light emitted from the diffraction patternof a fluorescent screen, that was measured by the photoreceptive meansafter the light passed through a halation-prevention filter that isvaried so that the transmittance when transmitting the visible lightemitted from the diffraction pattern of a fluorescent screen as theresult of the transmittance of the reflection high-energy electrondiffraction is minimum at the filter center and increases with thedistance from the center; an intensity decrease rate storage means thatstores the rate of decrease in the intensity of the visible light thatpasses through the halation-prevention filter; and a corrected-intensitycomputation means that computes the corrected intensity of thediffraction pattern by correcting the intensity stored by the measuredintensity storage means, based on the decrease rate stored by theintensity decrease rate storage means.

The present invention implements a measured intensity storage means thatstores the diffraction pattern intensity measured by the photoreceptivemeans after the light passes through the halation-prevention filter thatis varied so that the transmittance increases with the distance from thecenter; an intensity decrease rate storage means that stores the rate ofdecrease in the intensity of the visible light that passes through thehalation-prevention filter; and a corrected-intensity computation meansthat computes the corrected intensity of the diffraction pattern bycorrecting the intensity stored by the measured intensity storage means,based on the decrease rate stored by the intensity decrease rate storagemeans. So, it is possible to correct the intensity of the diffractionpattern obtained via the halation-prevention filter.

The invention implements an intensity measurement means that measuresthe intensity of the visible light emitted by the point light source,that is measured by the photoreceptive means, via thehalation-prevention filter that is changed so that the transmittancewhen transmitting the visible light emitted from the diffraction patternof the fluorescent screen as the result of the transmittance of thereflection high-energy electron diffraction is minimum at the filtercenter and increases with the distance from the center; an intensitydecrease rate computation means that computes the decrease rate, basedon the intensity measured by the intensity measurement means and thereference intensity of the visible light that is emitted from the pointlight source but does not pass through the halation-prevention filter;an intensity decrease rate storage means that stores the decrease ratecomputed by the intensity decrease rate computation means; a measuredintensity storage means that stores the intensity of the visible lightemitted from the diffraction pattern of the fluorescent screen, that ismeasured by the photoreceptive means, via the halation-preventionfilter; and a corrected-intensity computation means that computes thecorrected intensity of the diffraction pattern by correcting theintensity stored by the measured intensity storage means, based on thedecrease rate stored by the intensity decrease rate storage means.

The present invention implements an intensity measurement means thatmeasures the intensity of the point light source, that is measured bythe photoreceptive means, via the halation-prevention filter that ischanged so that the transmittance increases with the distance from thecenter; an intensity decrease rate computation means that computes thedecrease rate, based on the measured intensity and the referenceintensity of the point light source that does not pass through thehalation-prevention filter; an intensity decrease rate storage meansthat stores this decrease rate; a measured intensity storage means thatstores the diffraction pattern intensity measured by the photoreceptivemeans, via the halation-prevention filter; and a corrected-intensitycomputation means that computes the corrected intensity of thediffraction pattern, based on the decrease rate stored by the intensitydecrease rate storage means. So, it is possible to correct the intensityof the diffraction pattern obtained via the halation-prevention filter,according to the environment in which the halation-prevention filter isused. In this manner, the present invention attempts to achieve theaforementioned purposes.

Next, one embodiment of the present invention will be explained, withreference to FIGS. 1 and 2. Here, FIG. 1 is an overall schematic diagramof one example of the image analysis device 1 of the present embodiment.FIG. 2 is a photograph showing one example of halation-prevention filter12 used in image analysis device 1.

As shown in FIG. 1, the image analysis device 1 of the presentembodiment is equipped with photoreceptive means 11 that opticallyacquires the diffraction pattern that appears on the fluorescent screen24 for obtaining the diffraction pattern that results from reflectionhigh-energy electron diffraction as well as with halation-preventionfilter 12 that is provided, so as to transmit the visible light emittedfrom the diffraction pattern of the fluorescent screen, along the lightpath connecting the photoreceptive means 11 and the fluorescent screen24. Furthermore, in FIG. 1, A represents the diffraction pattern.

To explain this in detail, in FIG. 1, the reflection high-energyelectron diffraction device 2 is equipped with the vacuum chamber 22 inwhich is mounted the sample holder 21 that holds the measurement sample3, the electron gun 23 that exposes the measurement sample 3 to anelectron beam, and a fluorescent screen 24 on which appears thediffraction pattern resulting from the diffraction on the surface of themeasurement sample 3.

As aforementioned, the image analysis device 1 is equipped with thephotoreceptive means 11 that optically acquires the diffraction patternappearing on the fluorescent screen 24 and the halation-preventionfilter 12.

Here, the photoreceptive means 11 is the means of photographing, asmoving images or still pictures, the diffraction pattern appearing onthe fluorescent screen 24. Examples include a CCD camera, video camera,optical camera, etc. In photography by means of photoreceptive means 11,when conducting so-called in situ observation, which is used to observechanges in the crystal structures on the surface of the measurementsample 3 in the vacuum chamber, moving-picture photography is selected;when performing diffraction intensity analysis of the intensity of anobtained diffraction pattern, still-picture or moving-picturephotography is selected.

As aforementioned, the halation-prevention filter 12 is provided inorder to transmit the visible light emitted from the diffraction patternon the fluorescent screen, along the light path connecting thefluorescent screen 24 on which the diffraction pattern appears as theresult of reflection high-energy electron diffraction and thephotoreceptive means 11 that optically acquires the diffraction pattern.It is varied so that the transmittance of the visible light transmittedthrough the filter 12 is minimum at the filter center and increases withthe distance from the center. Furthermore, the transmittance indicateshow much incident light is transmitted. 100% transmittance meanstransmission without modification and without light intensity reduction.

To be specific, the transmittance of the filter 12 is set so as toincrease in proportion the r^(n), where r is the distance from thecenter of the filter 12. That is, when light of location-independent,uniform intensity is transmitted to the filter, in the observed plane,the transmittance of the light density at in-plane or in-planar distancer from the center correlates proportionally to r^(n).

The filter 12 is obtained by printing a gradient pattern on an opticallytransparent sheet or plate. Such a gradient pattern is readilyobtainable by means of fine computer graphics. For example, the filter12 can be fabricated by means of a technique that prints a gradientpattern on a transparent sheet.

One example of a concrete embodiment of this halation-prevention filter12 is shown in FIG. 2. As shown in FIG. 2, the filter 12 has a gradientpattern that varies from the center to the periphery. Here, the filter12 shown in FIG. 2 has the pattern that assumes that n=0.5, as thecorrelation with the aforementioned distance, and the transmittancegradient is such that the transmittance is lowest at the filter centerand the transmittance at distance r from the center is r^(0.5).

n=0.5 was derived as the result of tests conducted by the inventor ofthe present application, based on the fact that a CCD camera has a widerintensity dynamic range than does an optical camera. On the other hand,in the case of an optical camera, it is preferable to set n=3, as theattribute that maximizes the effectiveness of the filter 12.

Furthermore, as shown in FIG. 1, the filter 12 is positioned between thefluorescent screen 24 and a CCD camera, the photoreceptive means 11. Inthe present embodiment, if the fluorescent screen 24 has a diameterwithin the range from 100 mm to 200 mm, the distance from thefluorescent screen 24 to the CCD camera 11 is set within the range from200 mm to 500 mm.

Next, the process used to obtain the diffraction pattern in the presentembodiment will be explained. First, the measurement sample 3 to bemeasured is mounted in the sample holder 21. After the measurementsample 3 is placed in the sample holder 21, the interior of the vacuumchamber 22 is evacuated to the predetermined degree of vacuum. Then, themeasurement sample 3 is exposed to the incident electron beam from theelectron gun 23.

This incident electron beam is incident at a very small angle relativeto the measured surface of measurement sample 3. Then the incidentelectron beam is reflected and diffracted by the atoms near the surfaceof the measurement sample 3. The incident electron beam is incident at avery small angle, so the measurement is surface sensitive. The reflectedand diffracted electron beam produces an emission phenomenon in thefluorescent screen 24, so a spotted diffraction pattern corresponding tothe atomic structure in the vicinity of the surface appears on thefluorescent screen 24.

The diffraction pattern that appears on this fluorescent screen 24 isobtained optically, via the filter 12, by means of the photoreceptivemeans 11. When the diffraction pattern is obtained, it is also possibleto obtain in real time a sensitive diffraction pattern in the surfaceatomic structure of the measurement sample.

Here, when a photoreceptive means 11 (e.g., a CCD camera) that requiresfocusing is used, photographs are taken with the focus of the CCD camera11 set for the fluorescent screen 24, so the pattern of the filter 12does not appear directly on the photographed image. The decrease in theamount (i.e., intensity) of the visible light captured by the CCD camera11 is reflected in the image, in the shape corresponding to thetransmittance of the filter 12.

As a result, the CCD camera 11 is not focused on the filter 12, so evenif the gradient pattern's resolution is somewhat low, the low resolutionhas minimal effect on the image photographed through the filter 12. So,during the manufacture of the filter 12 of the present embodiment, highpattern precision is not required, so it can be manufactured easily andinexpensively, which can be considered an advantage.

As explained previously, in the present embodiment, by varying thefilter transmittance so that it is lowest at the filter center andincreases with the distance from the center, it is possible to minimizethe difference in intensity between the center and the peripheral areaby decreasing the intensity of the central area, even in diffractionpatterns with a high central intensity. Furthermore, even if the entirediffraction pattern is optically acquired, it is possible to provide anenvironment in which the entire, halation-free diffraction pattern canbe obtained.

Also, in the photoreceptive means, it is possible to control theintensity of the visible light emitted from the diffraction pattern ofthe fluorescent screen, within the allowable, halation-freephotoreceptive range.

Furthermore, because the transmittance increases in proportion to then^(th) power of r, the distance from the filter center, it is possibleto eliminate the smoothing of transmittance near the center, inintermediate regions, and elsewhere. Furthermore, it is possible to makethe transmittance highly distance dependent, so it is possible toeffectively and sufficiently reduce light intensity in the vicinity ofthe center, compared with that in the periphery.

Next, the second embodiment of the present invention will be explainedwith reference to FIG. 3. Here, components with the same structure as inthe aforementioned first embodiment are keyed with the same symbols, soredundant descriptions are omitted. FIG. 3 is the overall schematicdiagram showing the image analysis device 4 of the present embodiment.

In the present embodiment, the image analysis device 4 has, in additionto the configuration of the aforementioned first embodiment, thein-plane or in-planar movement means 13 and the in-plane or in-planarmovement means 14 that move the halation-prevention filter 12 in theplane orthogonal to the light path connecting the photoreceptive means11 and the fluorescent screen 24. However, in order to enable movementof the filter 12 to any in-plane or in-planar position, the in-plane orin-planar movement means 13 and the in-plane or in-planar movement means14 move the filter 12 in different directions.

Such an in-plane or in-planar movement means is provided because, in thenormal photography of reflection high-energy electron diffractionpatterns, the specular reflection point(s) are positioned about halfwayfrom the image center, so the position varies depending on thephotography conditions.

Next, the present embodiment will be explained in detail. As shown inFIG. 3, the image analysis device 4 of the present embodiment isequipped with the x-direction in-plane or in-planar movement means 13that moves the filter 12 in the x-direction in the figure and they-direction in-plane or in-planar movement means 14 that moves thefilter 12 in the y-direction in the figure, in the plane orthogonal tothe light path connecting the photoreceptive means 11 and thefluorescent screen 24.

The x-direction in-plane or in-planar movement means 13 is composed ofthe x-direction movement element 13 a that supports the filter 12, thex-direction lead screw shaft member 13 b, the x-direction drive motor 13c, and the x-direction lead screw shaft bearing 13 d.

Here, a through-hole is provided within the x-direction movement element13 a, and a female screw corresponding to the male screw part formed inthe surface of the x-direction lead screw shaft member 13 b is providedon the surface within this through-hole. Furthermore, one end of thex-direction lead screw shaft member 13 b is supported by the bearing 13d, and the other end is connected to the x-direction drive motor 13 c.This rotates forward and backward the x-direction drive motor 13 c,thereby controlling the movement of filter 12 in the x-direction.

Similarly, the y-direction in-plane or in-planar movement means 14 iscomposed of the y-direction movement element 14 a that supports thefilter 12, the y-direction lead screw shaft member 14 b, the y-directiondrive motor 14 c, and the y-direction lead screw shaft bearing 14 d.

A through-hole is provided within the y-direction movement element 14 a,and a female screw corresponding to the male screw part formed in thesurface of y-direction lead screw shaft member 14 b is provided on thesurface within this through-hole. Furthermore, one end of they-direction lead screw shaft member 14 b is supported by the bearing 14d, and the other end is connected to the y-direction drive motor 14 c.This rotates forward and backward the y-direction drive motor 14 c,thereby controlling the movement of filter 12 in the y-direction.

During the use of the image analysis device 4 of the present embodiment,the photoreceptive means 11 obtains the diffraction pattern bycontrolling the aforementioned x-direction in-plane or in-planarmovement means 13 and the y-direction in-plane or in-planar movementmeans 14, in order to align the center of the filter 12, wheretransmittance is lowest, with the position(s) of the specular reflectionpoint(s) of the diffraction pattern.

To be specific, while a fixed distance is maintained between thefluorescent screen 24 and the filter 12 and between the filter 12 andthe photoreceptive means 11, the x-direction drive motor 13 c and they-direction drive motor 14 c are rotated in order to move thex-direction movement element 13 a and the y-direction movement element14 a. For example, the filter position is set so that the filter centeris aligned with the specular reflection point(s) of the fluorescentscreen 24, when the diffraction pattern is viewed from thephotoreceptive means 11, while displaying the image photographed by thephotoreceptive means 11 on a monitor, etc. Then, the photoreceptivemeans 11 is used to photograph the diffraction pattern that appears onthe fluorescent screen 24, via the center-aligned filter 12.

As explained previously, in the present embodiment has in-plane orin-planar movement means 13 and 14, so it is possible to move the centerof the halation-prevention filter 12, thereby enabling the acquisitionof the diffraction pattern appropriate to the displacement of thespecular reflection point(s), which depends on the incident direction ofthe electron beam causing reflection high-energy electron diffraction.Furthermore, it is possible to provide an image analysis device 4equipped with a highly flexible halation-prevention mechanism.

Next, the third embodiment of the present invention will be explainedwith reference to FIG. 1 and FIGS. 4-6. Here, components with the samestructure as in the aforementioned embodiment are keyed with the samesymbols, so redundant descriptions are omitted. Also, FIG. 4 is aschematic diagram showing the image analysis device 5 of the presentembodiment. FIG. 5 is a functional block diagram of the diffractionpattern intensity correction means 16 equipped with the image analysisdevice 5. FIG. 6 is a data structure diagram of the measured intensitystorage means 35 equipped with the diffraction pattern intensitycorrection means 16. Furthermore, in FIG. 4, □ represents the pointlight source.

The present embodiment was invented based on the realization of the factthat it is effective to take into consideration the effect of the filter12 on the intensity of the visible light that is passed through thefilter 12, in order to increase the accuracy of the intensity analysisthat uses the image analysis device, when a configuration that preventshalation by obtaining a diffraction pattern through the filter 12 isadopted, as in the aforementioned first and second embodiments.

As shown in FIGS. 4 and 5, in addition to the basic structure (seeFIG. 1) of the reflection high-energy electron diffraction device 2 withfluorescent screen 24 that was explained in the aforementioned firstembodiment, the image analysis device 5 of the present embodiment isequipped with the photoemissive means 15 that generates the point lightsource, the emission control means 31 that controls the generation ofthe point light source of the photoemissive means 15, the intensitymeasurement means 32 that measures, via the photoreceptive means 11, theintensity through the filter 12 of the visible light emitted from thediffraction pattern of the fluorescent screen and the intensity throughthe filter 12 of the visible light emitted by the point light source,the intensity decrease rate computation means 33 that computes the rateof decrease in the intensity of the visible light transmitted throughthe filter 12, based on the intensity of the visible light emitted bythe point light source, that was measured by the intensity measurementmeans 32, and the corrected-intensity computation means 36 that computesthe corrected intensity obtained by correcting the intensity, asmeasured by the photoreceptive means 11, of the visible light emittedfrom the diffraction pattern of the fluorescent screen, based on thedecrease rate computed by the intensity decrease rate computation means33.

To be more specific, the photoemissive means 15 is the means (e.g., aliquid-crystal panel) of generating a point light source at anyposition, under the control of the emission control means 31 describedlater. As shown in FIG. 4, it is desirable to provide a detachablephotoemissive means 15 where the fluorescent screen 24 is configured inthe first embodiment. This is done in order to obtain the correctionparameters in the environment in which the diffraction pattern isactually obtained, thereby enabling the most accurate correction.

Here, when adopting a method of mounting the photoemissive means 15 atthe location where the fluorescent screen 24 is placed (e.g., byoverlapping the fluorescent screen 24 with the photoemissive means 15),it is necessary to minimize the measurement condition error caused by animperfect alignment with the placement position of the fluorescentscreen 24. Concretely, the condition should be that [the error] iswithin the error range that is allowable in the later-mentionedcorrection, which takes into consideration the intensity decrease.

That is, as shown in FIG. 4, the distance between the photoemissivemeans 15 and the photoreceptive means 11 is adjusted so that it equalsthe distance (see FIG. 1) between the photoreceptive means 11 and thefluorescent screen 24 when obtaining the diffraction pattern, and thespacing between the photoreceptive means 11 and filter 12 whenphotographing the point light source is adjusted so that it equals thedistance between the photoreceptive means 11 and the filter 12 whenobtaining the diffraction pattern. However, it also is possible to adopta method that approximates the corrected intensity, by adopting aconfiguration that yields an interrelationship similar to the positionalrelationship among the fluorescent screen 24, the filter 12, and thephotoreceptive means 11.

Also, the emission control means 31, the intensity measurement means 32,the intensity decrease rate computation means 33, the intensity decreaserate storage means 34, the measured intensity storage means 35, and thecorrected-intensity computation means 36 shown in FIG. 5 are implementedby the processing means and the storage means (not shown) that areprovided in the diffraction pattern intensity correction means 16, whichis equipped with the image analysis device 5. Furthermore, as thediffraction pattern intensity correction means 16 equipped with thesemeans, an information processing device (e.g., a personal computer) thatalso analyzes the image information obtained by the photoreceptive means11 is assumed.

The storage means is the means of storing information in a given region.Examples include so-called memory (e.g., RAM), storage media (e.g., HDD,CD-R), etc. However, it is not limited to a specific medium, and aconfiguration that combines multiple storage media may also be used.

Also, the processing means is a means of processing information thatincludes a computation means (e.g., a CPU), and it controls operationssuch as the input/output interface (not shown) that receives imageinformation from the photoreceptive means and the aforementioned storagemeans, etc. However, it is not limited to a configuration that consistssolely of one specific computation means, but it also may be configuredwith multiple computation means that enable the parallel processing ofinformation.

The processing means implements the aforementioned emission controlmeans 31, the intensity measurement means 32, the intensity decreaserate computation means 33, and the corrected-intensity computation means36, when processing is initiated by external commands, etc., accordingto the diffraction pattern intensity correction program stored in aspecific region of the storage means.

Here, the emission control means 31 is the means of controlling thegeneration of the point light source in the photoemissive means 15. Bycontrolling so that the emission control means 31 emits light of aspecific intensity at any point of the photoemissive means 15, it ispossible to set at any position the point light source that emits thereference intensity, which is the reference for computing the intensitydecrease rate mentioned later.

The intensity measurement means 32 is the means of obtaining theintensity (i.e., amount) of visible light at a specific point in theimage information, based on the image information obtained by thephotoreceptive means 11. The intensity measurement means 32 is used tomeasure not only the intensity of the light emitted by the point lightsource, but also to measure the intensity of the light emitted from thediffraction pattern of the aforementioned fluorescent screen.

The intensity decrease rate computation means 33 is the means ofcomputing the rate of decrease in the point light source intensity,which is reduced by passing through the filter. Here, the intensitydecrease rate is the parameter that represents how much the lightemitted at any position is decreased by passing through the filter 12with a varied transmittance, and it means that, when the intensitydecrease rate is 0%, the intensity is not reduced by the filter 12, sothe light intensity is not attenuated.

To be more specific, based on the point light source intensity measuredby the intensity measurement means 32 and the theoretical or measuredreference intensity of the visible light emitted by the point lightsource when it did not pass through the halation-prevention filter 12,the means computes how much the intensity of the visible light dropsafter passing through the filter 12, compared with the case where thefilter 12 is not provided.

The intensity decrease rate storage means 34 is the means of storing theintensity decrease rate computed by the intensity decrease ratecomputation means 33, in predetermined areas in the aforementionedstorage means (not shown), and it stores the intensity decrease rate byassociating it with the point light source position (i.e., the specificpositional coordinates on the fluorescent screen 24).

The measured intensity storage means 35 is the means of storing theintensity of the visible light emitted from the target, that is measuredby the photoreceptive means 11, in a specific area in the aforementionedstorage means (not shown). In the present embodiment, the intensitymeasurement means 32 stores the intensity of the diffraction pattern incases where the diffraction pattern is measured after the light passesthrough the filter 12.

The corrected-intensity computation means 36 is the means of computingcorrected intensities, for the intensities of the diffraction patternsstored by the measured intensity storage means 35, based on theintensity decrease rates stored by the intensity decrease rate storagemeans 34.

Furthermore, the external device 17 shown in FIG. 5 is a device that isconnected to the diffraction pattern intensity correction means 16 andthat receives the intensities of diffraction patterns after correctionsobtained by means of the diffraction pattern intensity correction means16. Examples include display monitors, other measuring instruments, etc.

By adopting the configuration of the present embodiment, it is possibleto provide an environment that enables the acquisition of the intensityof the visible light actually emitted from the diffraction pattern ofthe fluorescent screen and enables the accurate analysis of theintensity, because the rate of decrease in the intensity of the visiblelight that passed through the filter is computed and, based thereupon,the corrected intensity, which is determined by correcting the intensityof the visible light emitted from the diffraction pattern of thefluorescent screen, is computed.

Also, the diffraction pattern intensity analysis of the presentembodiment analyzes the intensity of the visible light emitted from thediffraction pattern of the fluorescent screen as the result ofreflection high-energy electron diffraction. Also, as the diffractionpattern intensity analysis method, a method with the following processeswas adopted: a process that utilizes the photoreceptive means 11 tomeasure the intensity of the diffraction pattern that appears on thefluorescent screen 24, via the halation-prevention filter 12 that isvaried so that the transmittance is lowest at the center of the filter12 and increases with the distance from the center; a process thatutilizes the photoreceptive means to measure the intensity of the pointlight source via the filter, and then obtains the rate of decrease inthe intensity of the visible light transmitted through the filter, basedon the measurement results; and a process that corrects the diffractionpattern intensity measured by the photoreceptive means, based on thedecrease rate.

When such a diffraction pattern intensity analysis method is adopted, itis possible to obtain the intensity of the visible light actuallyemitted from the diffraction pattern of the fluorescent screen, becauseit has a process that measures the intensity of the diffraction pattern,through the halation-prevention filter that is varied so that thetransmittance increases with the distance from the center, a processthat obtains the rate of intensity decrease caused by the filter, and aprocess that corrects the intensity of the diffraction pattern based onthe decrease rate. Furthermore, accurate intensity analysis is possible.

Next, the diffraction pattern intensity correction program thatimplements the aforementioned emission control means 31, the intensitymeasurement means 32, the intensity decrease rate computation means 33,the corrected-intensity computation means 36, etc., will be explained indetail.

The diffraction pattern intensity correction program of the presentembodiment implements the intensity measurement means 32 that measuresthe intensity of the visible light that is emitted by the point lightsource and is measured by the photoreceptive means 11, via thehalation-prevention filter 12 that is varied so that the transmittancewhen transmitting the visible light emitted from the diffraction patternof the fluorescent screen as the result of the transmittance of thereflection high-energy electron diffraction is minimum at the filtercenter and increases with the distance from the center; the intensitydecrease rate computation means 33 that computes the decrease rate,based on the intensity measured by the intensity measurement means 32and the reference intensity of the visible light that is emitted by thepoint light source but does not pass through the halation-preventionfilter 12; the intensity decrease rate storage means 34 that stores thedecrease rate computed by the intensity decrease rate computation means33; the measured intensity storage means 35 that stores the intensity ofthe visible light emitted from the diffraction pattern of thefluorescent screen, that passes through the halation-prevention filter12 and is measured by the photoreceptive means 11; and thecorrected-intensity computation means 36 that computes the correctedintensity of the diffraction pattern, by correcting the intensity storedby the intensity storage means 35, based on the decrease rate stored bythe intensity decrease rate storage means 34.

To be specific, the processing based on the aforementioned diffractionpattern intensity correction program is as follows: For light emittedfrom any point (x, y) on the fluorescent screen 24, the intensitydecrease rate T(x, y) of the filter following measurement by using thephotoreceptive means 11 is determined. Then the transmission-correctedintensity I(x, y) is determined based on the diffraction pattern'sintensity I_(C)(x, y), which was measured by using the photoreceptivemeans 11.

Hereinafter, processing based on the diffraction pattern intensitycorrection program is divided broadly into processing that computes theintensity decrease rate and processing the corrects the diffractionpattern intensity.

First, the sequence of processes used to compute the intensity decreaserate will be explained. The intensity decrease rate computation means 33initially determines the intensity I_(O) of the point light source usedas the reference, after which it transfers the instruction informationto the emission control means 31, in order to generate a point lightsource of that intensity. Based on the transferred instructioninformation, the emission control means 31 sends control information tothe photoemissive means 15, in order to generate the point light sourceemitted at given intensity I_(O) at given position (x1, y1). Based onthe sent control information, the photoemissive means 15 generates thereference point light source at the given position (x1, y1).

Then, the intensity measurement means 32 measures the intensityI_(OC)(x1, y1) of the point light source generated by the photoemissivemeans 15, via the photoreceptive means 11, with the transmittance-variedfilter installed. Subsequently, the intensity measurement means 32stores the measured intensity I_(OC)(x1, y1) of the point light sourcein a given region of the storage means, after which it transfers thestored intensity I_(OC)(x1, y1) to the intensity decrease ratecomputation means 33.

The intensity decrease rate computation means 33 that received theintensity I_(OC)(x1, y1) (i.e., the measurement result) computes theintensity decrease rate T(x1, y1), based on the intensity I_(O)transferred to the emission control means 31 and the received intensityI_(OC)(x1, y1). The intensity decrease rate computation means 33transfers the computed intensity decrease rate T(x1, y1) to theintensity decrease rate storage means 34.

Subsequently, the intensity decrease rate storage means 34 stores byassociating the intensity decrease rate T(x1, y1) computed by theintensity decrease rate computation means 33 and the positioncoordinates (x1, y1). Finally, intensity decrease rate storage means 34stores the intensity decrease rate T(x_(i), y_(i)) for each differentposition coordinates (x_(i), y_(i)) and functions as the database ofintensity decrease rates when the filter 12 is used.

Next, the relationship among the point light source's measured intensityI_(OC)(x_(i), y_(i)), the reference intensity I_(O), and the intensitydecrease rate T(x_(i), y_(i)) is as shown in the following Equation 1.T(x _(i) , y _(i))=I _(OC)(x _(i) , y _(i))/I _(O)  (1)

Furthermore, for the position coordinates (x_(i), y_(i)), thefluorescent screen 24 of the reflection high-energy electron diffractiondevice 2 is provided. Also, they may be expressed as the absolutecoordinates of the installation surface 25 on which the photoemissivemeans 15 is installed or they may be expressed as the relativecoordinates from the center of the filter 12.

The aforementioned are the series of processes used to compute theintensity decrease rate by using a point light source. Hereinafter, thepresent invention evolves into a series of processes used to correct theintensity of the diffraction pattern, by using the computed intensitydecrease rate. The process used to correct the intensity of adiffraction pattern will be explained next.

First, as in the aforementioned embodiment, the diffraction pattern isacquired optically, via photoreceptive means 11, while using filter 12.This diffraction pattern is obtained under the control of the intensitymeasurement means 32. The intensity measurement means 32 transfers themeasured intensity I_(C)(x_(i), y_(i)) of the diffraction pattern andits position coordinates (x_(i), y_(i)) to the measured intensitystorage means 35.

As shown in FIG. 6, the measurement intensity storage means 35 stores byassociating the measured intensity I_(C)(x_(i), y_(i)) and the positioncoordinates (x_(i), y_(i)). Furthermore, although many measuredintensities I_(C) are preferable, it is suffices to measure according tothe position of the luminescent spot of the diffraction pattern targetedfor analysis.

Then, the corrected intensity computation means 36 receives the measuredintensity I_(C)(x_(i), y_(i)) and the position coordinates (x_(i),y_(i)) from the measured intensity storage means 35 and receivesintensity decrease rate T(x_(i), y_(i)) from the intensity decrease ratestorage means 34, after which it computes the corrected intensityI(x_(i), y_(i)) (i.e., the actual intensity), with the received positioncoordinates (x_(i), y_(i)) as the index. Then, the corrected-intensitycomputation means 36 transfers the corrected intensity I(x_(i), y_(i))to the external device 17, such as a display monitor or anothermeasuring instrument.

Here, the relationship among the measured diffraction pattern's measuredintensity I_(C)(x_(i), y_(i)) and intensity decrease rate T(x_(i),y_(i)) and the corrected diffraction pattern's intensity I(x_(i), y_(i))is as shown in the following Equation 2.I(x _(i) , y _(i))=I _(C)(x _(i) , y _(i))×T(x _(i) , y _(i))  (2)

As explained previously, the present embodiment implements the intensitymeasurement means 32 that measures the intensity of the point lightsource measured by the photoreceptive means 11, via thehalation-prevention filter 12 that is varied so that its transmittanceincreases with the distance from the center, the intensity decrease ratecomputation means 33 that computes the decrease rate based on themeasured intensity and the reference intensity of the point light sourcewhen it does not pass through the halation-prevention filter 12, theintensity decrease rate storage means 34 that stores the decrease rate,the measured intensity storage means 35 that stores the diffractionpattern intensity measured by the photoreceptive means 11, via thehalation-prevention filter 12, and the corrected-intensity computationmeans 36 that computes the corrected intensity of the diffraction basedon the decrease rate stored by the intensity decrease rate storage means34, thereby enabling the correction of the diffraction pattern intensityobtained via the halation-prevention filter 12, according to theenvironment in which the halation-prevention filter 12 is used, andthereby enabling the acquisition of the precisely corrected orcalibrated intensity of the visible light actually emitted from thediffraction pattern of the fluorescent screen.

Here, the present embodiment is not limited to the aforementionedembodiments. For example, the correction of the diffraction patternintensity by means of the aforementioned procedure is not limited to thecorrection of intensity information represented by numbers of a specificunit system (e.g., candela), based on the obtained decrease rate.Instead of correcting numbers, it also is possible to correct theoptical intensity information by, for example, subjecting to imageprocessing the image information itself that indicates the diffractionpattern, based on the obtained decrease rate.

Also, although the present embodiment adopted a configuration that isbased on the first embodiment and is equipped with the photoemissivemeans 15, the diffraction pattern intensity correction means 16, etc.,based on the first embodiment, it also is possible to substitute aconfiguration that is based on the second embodiment and is equippedwith the photoemissive means 15, the diffraction pattern intensitycorrection means 16, etc.

Moreover, the aforementioned diffraction pattern intensity correctionprogram is not limited to a form such that it is installed in aso-called preinstalled form on a storage means (e.g., HDD). It also maybe in the form such that it is stored in a compressed form as aninstallable program on a portable storage medium (e.g., CD-ROM,DVD-ROM), or in which it is installed as required on equipment (e.g., apersonal computer).

The deformation or distortion example of the aforementioned thirdembodiment will be explained with reference to FIG. 7. Here, componentswith the same structure as in the aforementioned embodiment are keyedwith the same symbols, so redundant descriptions are omitted. Also, FIG.7 is a functional block diagram of the diffraction intensity correctionmeans 18 of the present deformation example.

The present deformation example resulted from focusing on the fact thatintensity analysis can be facilitated by adding, to a any commercialintensity analysis program (i.e., software), a routine that corrects theintensity by using an equation with terms I(x, y) and T(x, y), asexplained in a previous embodiment.

In an image analysis device for the filter 12, that does not requireactual measurement for intensity correction when, for example, thepredetermined specifications (e.g., the lens aperture and resolution ofthe photoreceptive means 11) are already clear, it is possible to adopta packaged configuration that embeds the correction details as defaults.

To be specific, as shown in FIG. 7, as the aforementioned deformationexample of the third embodiment, the intensity correction program may beone that utilizes, via a halation-prevention filter (not shown) thatvaries the transmittance when transmitting the visible light emittedfrom the diffraction pattern of the fluorescent screen as the result ofreflection high-energy electron diffraction, so that it is minimal atthe filter center and increases with the distance from the center, thediffraction pattern intensity correction means 18 that implements themeasured intensity storage means 35 that stores the intensity, asmeasured by the photoreceptive means 11, of the visible light emittedfrom the diffraction pattern of the fluorescent screen, the intensitydecrease rate storage means 37 that stores the rate of decrease of theintensity of the visible light transmitted through thehalation-prevention filter, and the corrected-intensity computationmeans 36 that computes the corrected intensity of the diffractionpattern by correcting the intensity stored by the measured intensitystorage means 35, based on the decrease rate stored by the intensitydecrease rate storage means 37.

Here, as aforementioned, the intensity decrease rate storage means 37stores, as default correction parameters, the intensity decrease ratesappropriate to the specifications and the preset data for thehalation-prevention filter and the photoreceptive means 11. Furthermore,regarding the data structure of this intensity decrease rate storagemeans 37, the adopted structure is such that the intensity decrease rateT(x_(i), y_(i)) and the position coordinates (x_(i), y_(i)) are related,instead of the measured intensity I(x_(i), y_(i)) shown in FIG. 6.

Even if such a deformation example is used, it is possible to correctthe intensity of the diffraction pattern obtained via thehalation-prevention filter and it is possible to obtain the intensity ofthe visible light actually emitted from the diffraction pattern of thefluorescent screen, because the following are implemented via ahalation-prevention filter (not shown) that is varied so that thetransmittance increases with the distance from the center: the measuredintensity storage means 35 that stores the diffraction pattern intensitymeasured by the photoreceptive means 11, the intensity decrease ratestorage means 37 that stores the rate of decrease in the intensity ofthe visible light transmitted through the halation-prevention filter,and the corrected-intensity computation means 36 that computes thecorrected intensity for the diffraction pattern by correcting theintensity stored by the measured intensity storage means 35, based onthe decrease rate stored by the intensity decrease rate storage means37. Furthermore, it provides an environment in which accurate intensityanalysis can be performed simply.

Next, comparative examples of the use and nonuse of the previouslydescribed halation-prevention filter will be explained, with referenceto FIGS. 8 and 9. FIG. 8 is a photograph taken with a CCD camera bymeans of a conventional method that does not use a halation-preventionfilter, of the reflection high-energy electron diffraction pattern of anSi(111) single-crystal clean surface. FIGS. 8(a), 8(b), and 8(c) arephotographs taken with different exposure times. Meanwhile, FIG. 9 is aphotograph of the reflection high-energy electron diffraction pattern ofa Si(111) single-crystal clean surface, which was taken with a CCDcamera while using a halation-prevention filter.

FIG. 8(a) is the diffraction pattern obtained with a 0.5-sec. exposuretime. FIG. 8(b) is the diffraction pattern obtained with a 1-sec.exposure time. FIG. 8(c) is the diffraction pattern obtained with a2-sec. exposure time. Furthermore, the same diffraction patternnaturally is used as the target diffraction pattern.

In FIG. 8(a), the exposure time was insufficient, so there was nohalation in the vicinity of the specular reflection point(s). However,because the Kikuchi pattern outside the first Laue zone is dark as theresult of insufficient exposure, it cannot be determined.

If the exposure time is lengthened in order to determine the Kikuchipattern outside the first Laue zone, the variation is as shown in FIGS.8(b) and (c). To be specific, as shown in FIG. 8(b), when the exposuretime is lengthened to 1 sec., the Kikuchi pattern in the vicinity of thefirst Laue zone becomes identifiable. However, halation occurs in thevicinity of the specular reflection point(s). Furthermore, when theexposure time is set to 2 sec. in order to verify the second Laue zone,etc., not only the vicinity of the specular reflection point(s), butalso the inside of the zero-order Laue zone becomes completely halated,as shown in FIG. 8(c).

By contrast, FIG. 9 shows the diffraction pattern when using ahalation-prevention filter with the filter gradation variation gradient(i.e., the transmittance variation) set to n=0.5. Furthermore, thephotographed diffraction pattern is the same as the diffraction patternin FIG. 8, and the CCD camera used for photography is also the same.

Then, under the conditions shown in the aforementioned FIG. 8, halationinitially occurred in the vicinity of the specular reflection point(s).In view of this, when the diffraction pattern shown in FIG. 9 wasphotographed, the exposure time was set so that halation did not occurin the vicinity of the specular reflection point(s), as a comparativeexample for the photograph shown in FIG. 8. Furthermore, the exposuretime was 4 sec.

As shown in FIG. 9, when a halation-prevention filter was used, it waspossible to clearly photograph up to the Kikuchi pattern that appearedoutside the second Laue zone, while maintaining a visible lightintensity in the vicinity of the specular reflection point(s), that wassimilar to that in FIG. 8(a).

The present invention is configured and functions as aforementioned, byvarying the filter transmittance so that it is lowest at the filtercenter and increases with the distance from the center, it is possibleto supply an environment that yields the entire diffraction patternwithout halation, even though the entire diffraction pattern is acquiredoptically.

Also, because the transmittance increases in proportion to the n^(th)power of r, the distance from the filter center, it is possible toeffectively and adequately reduce the light intensity in the vicinity ofthe center, compared with that in the periphery.

Furthermore, by varying the filter transmittance so that it is lowest atthe filter center and increases with the distance from the center, it ispossible in the photoreceptive means to obtain the intensity of thevisible light emitted from the diffraction pattern on the fluorescentscreen, within the allowable range of halation-free photoreception.

Also, because the transmittance increases in proportion to the n^(th)power of r, the distance from the filter center, it is possible toeffectively and adequately reduce the light intensity in the vicinity ofthe center, compared with that in the periphery.

The invention also has an in-plane or in-planar movement means, so itcan provide a highly flexible halation-prevention mechanism that canrespond to displacement of the specular reflection point(s) of thediffraction pattern.

The invention may provide an environment that enables accurate intensityanalysis, because the rate of decrease in the intensity of the visiblelight transmitted through the filter is computed, and the correctedintensity resulting from the correction of the intensity of the visiblelight emitted from the diffraction pattern on the fluorescent screen iscomputed based on the decrease rate.

Also, the invention may provide a diffraction pattern intensity analysismethod that enables accurate intensity analysis, because it is equippedwith a process that measures the intensity of a diffraction pattern viaa halation-prevention filter that is varied so that the transmittanceincreases with the distance from the center, a process that obtains theintensity decrease rate attributable to the filter, and a process thatcorrects the intensity of the diffraction pattern, based on the decreaserate.

In the present invention, because the transmittance increases inproportion to the nth power of r, the distance from the filter center,it is possible to provide a diffraction pattern intensity analysismethod that can analyze, without halation, the intensity of the visiblelight emitted from the diffraction pattern of a fluorescent screen.

Also, the invention implements a measured intensity storage means thatstores the intensity of the diffraction pattern measured by thephotoreceptive means, via the halation-prevention filter varied so thatthe transmittance increases with the distance from the center, anintensity decrease rate storage means that stores the rate of decreasein the intensity of visible light transmitted through thehalation-prevention filter, and a corrected-intensity computation meansthat computes the corrected intensity of a diffraction pattern bycorrecting the intensity stored by the measured intensity storage meansbased on the decrease rate stored by the intensity decrease rate storagemeans, thereby making it easy to obtain the intensity of the visiblelight actually emitted from the diffraction pattern of the fluorescentscreen. Furthermore, it can provide simply an environment that enablesaccurate intensity analysis.

Furthermore, the invention implements an intensity measurement meansthat measures the intensity of the point light source measured by thephotoreceptive means, via the halation-prevention filter varied so thatthe transmittance increases with the distance from the center, anintensity decrease rate computation means that computes the decreaserate based on the measured intensity and the reference intensity of thepoint light source when it does not pass through the halation-preventionfilter, an intensity decrease rate storage means that stores itsdecrease rate, a measured intensity storage means that stores theintensity of the diffraction pattern measured by a photoreceptive means,via the halation-prevention filter, and a corrected-intensitycomputation means that computes the corrected intensity of a diffractionpattern based on the decrease rate stored by the intensity decrease ratestorage means, so it enables the determination of the preciselycorrected intensity of the visible light actually emitted from thediffraction pattern of the fluorescent screen.

Accordingly, it is to be understood that the embodiments of theinvention herein described are merely illustrative of the application ofthe principles of the invention. Reference herein to details of theillustrated embodiments is not intended to limit the scope of theclaims, which themselves recite those features regarded as essential tothe invention.

1. A diffraction pattern intensity analysis method used to analyzeintensity of visible light emitted from a diffraction pattern of afluorescent screen as a result of reflection high-energy electrondiffraction, comprising the steps of: using a photoreceptor to measurethe intensity of the diffraction pattern that appears on the fluorescentscreen, via a halation-prevention filter with a transmittance which isminimum at a filter center and increases with distance from the filtercenter; based on a result of the measurement, obtaining a rate ofdecrease in the intensity of the visible light transmitted through thefilter; and correcting the diffraction pattern intensity measured by thephotoreceptor, based on the decrease rate.
 2. The diffraction patternintensity analysis method of claim 1, in which the transmittance ofvisible light transmitted through the filter increases in proportion tor^(n), where r is a distance from the filter center.
 3. A diffractionpattern intensity correction program for use with an image analysisdevice having a fluorescent screen for creating a diffraction patternthat results from reflection high-energy electron diffraction, aphotoreceptor for optically acquiring the diffraction pattern thatappears on the fluorescent screen, and a halation-prevention filter forlocation along a light path connecting the fluorescent screen and thephotoreceptor, in which a transmittance of the visible light transmittedthrough the filter is minimum at a center of the filter and increaseswith a distance from the center, the program comprising: a measuredintensity storage means for storing an intensity of visible lightemitted from the diffraction pattern on the fluorescent screen as aresult of reflection high-energy electron diffraction, passed throughthe halation-prevention filter and detected by the photoreceptor means;an intensity decrease rate storage means for storing a rate of decreasein the intensity of the visible light transmitted through thehalation-prevention filter; and a corrected-intensity computation meansfor computing a corrected intensity of the diffraction pattern bycorrecting the intensity stored by the measured intensity storage means,based on the decrease rate stored by the intensity decrease rate storagemeans.
 4. The diffraction pattern intensity correction program of claim3, further comprising: a point light source; an emission controller forcontrolling the generation of light by the point light source; anintensity measurement means for measuring, via the photoreceptor, theintensity of the visible light emitted from the diffraction pattern ofthe fluorescent screen and the intensity of the point lightsource-emitted visible light that passed through the filter; anintensity decrease rate computation means for computing a rate ofdecrease in the intensity of the visible light transmitted through thefilter, based on the intensity of the visible light emitted by the pointlight source, that was measured by the intensity measurement means; anda corrected-intensity computation means that, based on the decrease ratecomputed by the intensity decrease rate computation means, computes thecorrected intensity used to correct the intensity of the visible lightemitted from the diffraction pattern of the fluorescent screen, that wasmeasured by the photoreceptor.